Histogram Generating Circuit Memory Optimization
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Solution Overview
Problem
Existing histogram generating circuits for optical rangefinders waste memory capacity due to the need for a memory area corresponding to the number of time bins, and the memory capacity increases wastefully with higher ranging resolution and longer measurement distances.
Innovation Solution
A histogram generating circuit that associates bin numbers with flight information and cumulative frequencies, allowing for efficient storage in a memory circuit without pre-allocating memory for bins with no occurrences, and utilizing a FIFO-type memory circuit to buffer flight information and update histograms asynchronously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the address of the memory is associated with the timer value measured by the timer unit, then the histogram can be generated covering the entire time range, but the memory area with no time value present is wasted
Solution Approach 1:
The patent extracts the timer value from the memory address association and uses it only for sorting and identifying flight information. The memory address is instead associated with bin numbers that are assigned sequentially based on sorted flight information, eliminating the need to allocate memory for all possible timer values including those with no occurrences.
Solution Approach 2:
The patent implements dynamic bin number assignment where bin numbers are assigned sequentially based on sorted flight information rather than being fixed by timer value ranges. This dynamic approach allows the memory structure to adapt to the actual distribution of flight information, allocating memory only where data exists.
2Measurement precision
If the total number of bins and data bit width of the bin increase to achieve higher ranging resolution and longer measurement distance, then the measurement capability is improved, but the memory capacity wastefully increases
Solution Approach 1:
The patent applies partial action by only creating bins for timer values that actually have flight information occurrences. Instead of pre-allocating memory for all possible bins required by the maximum measurement range and resolution, the system dynamically creates only the necessary bins based on actual data distribution, reducing memory usage while maintaining the required measurement capability.
3Ease of operation
If a memory area corresponding to the number of time bins is prepared in advance, then the histogram generation can be simplified, but the memory capacity increases even for bins with no occurrences
Solution Approach 1:
The patent performs preliminary sorting of flight information by timer value before histogram generation. This preliminary action organizes the data in advance, allowing the subsequent histogram generation to simply iterate through the sorted data and assign bin numbers sequentially, eliminating the need for pre-allocated memory while maintaining operational simplicity.
Data Source
AI summary
A histogram generating circuit generates a histogram based on respective flight information that is a time of flight or a flight distance from an emission time point of measurement light repeatedly emitted at predetermined periods to a detection time point of reflected light for respective measurement light, the histogram showing a cumulative frequency of the flight information distributed in a preset measurement range, the histogram generating circuit including: a memory circuit configured to store the histogram; and a memory processing circuit configured to associate a bin number for identifying each bin obtained by splitting the measurement range into a plurality of divisions individually in order based on the flight information with the flight information contained in each bin and the cumulative frequency, and store them in the memory circuit, thereby effectively using a limited memory area.